No HE sensor. You use another o2 sensor. You calculate the displacement of o2 with helium. So if first mixing chamber sensor reads 10.5, you have 50% helium. Then you add o2 back in the 2nd mixing chamber. At least that is what I have been told. It has been a long time since I took the blending course and since I don’t have a reason to dive trimix up here I have since forgotten most of the more advanced calculations.
I’m using the old R-22D sensors out of my O2ptima CM. instead of throwing them away, I just trickle them down. 1 year in rebreather, 1 year in the mixing stick and my divesoft analyzer. Then garbage.
